The invention is based on a drive shaft for a windshield wiper.
Known windshield wipers have a wiper arm, which is constructed from a fastening part and a hinge part, pivotably connected to it via a foldaway joint, and having a wiper rod. A hooklike end of the wiper rod engages a suspension box of a wiper blade, which is formed by two side cheeks of a middle bracket and includes a connection part with a hinge bolt. The joint thus formed guides the wiper blade over the vehicle window during the pivoting motion.
The wiper arm is connected via its fastening part solidly but detachably to a drive shaft. The drive shaft protrudes from the vehicle body and on its free shaft end it has an outer cone, which cooperates with an inner cone on the fastening part, in that a screw nut firmly presses the conical parts together. The drive shaft is as a rule made from steel and is riveted to a crank on its drive-side end.
From German Patent Disclosure DE 44 28 371 A1, a shaft hub connection of a windshield wiper is known in which the drive shaft, in the connecting region with the fastening part, has a cross section other than circular, and in particular a polygonal cross section, and has a shoulder. The fastening part rests with one edge of a recess on the shoulder or on a shim, and the recess widens conically toward the end of the drive shaft. A fitting conical clamping part is inserted into the recess and is pressed against the fastening part by a screw nut. The clamping part has a passageway for the drive shaft, and the cross-sectional profile of the passageway is complimentary to that of the drive shaft.
A shaft hub connection of a windshield wiper is also known from U.S. Pat. No. 3,085,821. The fastening part rests with one edge of a recess on a shoulder of the drive shaft or a shim, and the recess widens conically toward the end of the drive shaft. A fitting conical clamping part is inserted into the recess and presses a screw nut against the fastening part. The clamping part has a passageway for the drive shaft that fits a cylindrical or conical region of the drive shaft with knurling or a zigzag surface. As a result of the conical connection between the fastening part and the clamping part and optionally the conical connection between the clamping part and the drive shaft, the zigzag surface of the fastening part and of the drive shaft is pressed into what until then was a largely smooth surface of the clamping part and deforms it permanently. To that end, the clamping part comprises an elastomer material or a relatively soft nonferrous metal. In addition to a nonpositive engagement, a reinforcing positive engagement is achieved by means of many small side faces of the zigzags.
From German Utility Model DE 89 13 885 U1, it is known to dispose a spray nozzle on a housing of a wiper bearing. A water conduit extends parallel to the drive shaft through the bearing housing to the spray nozzle.
French Patent Disclosure FR 2 646 801 A shows a windshield wiper with a wiper arm and a wiper blade of plastic. The wiper arm has a hollow profile and is made by an internal gas pressure process. One version has a hinge part with a formed-on hollow wiper rod, and the hollow space is part of a windshield washer and has spray holes that are aimed at the windshield. In a variant, the wiper arm has no hinge part; instead, the wiper rod is formed directly onto the fastening part. The washing fluid is delivered through the drive shaft here.
According to the invention, the base body of the drive shaft is made from an extruded light metal profile. On its free end in the region of a fastening part, it has a connection part of a harder material, which has a screw thread. As the material, steel will be considered primarily, but other materials are also fundamentally suitable, such as copper and bronze.
The drive shaft of the invention is very light in weight and can be produced economically in many variants. For instance, for receiving a fastening part, the connection part can have a conical seat with fluting or with a polygonal slaving profile, and the material can be adapted optimally to the increased demands in terms of pressure per unit of surface area, wear resistance, and mounting capability. Thus reliable, easily released seating of the fastening part is assured even after frequent assembly and disassembly.
The connection part is expediently connected by means of adhesive bonding, welding, pressing, or assembly casting. To that end, a conical protrusion on the base body is advantageous. On the one hand, it facilitates centering of the two parts to one another; on the other hand, it makes a large joining area possible, by way of which the forces and torques are readily transmitted.
For the assembly casting, the connection part is placed on the base body, and the adjoining gap is filled by injection of liquid zinc, magnesium, lead, tin, or a suitable alloy. An adapter piece of zinc or a suitable material can be disposed between the base body and the connection part and can penetrate the base body or connection part. The adapter piece is expediently also seated on a longitudinally fluted, conical protrusion of the base body and itself has a fluted cone for receiving the connection part.
The drive shaft, comprising a base body, optionally an adapter piece and the connection part, can, without substantial additional cost, have one or more longitudinal conduits, through which washing fluid can be carried to spray nozzles, which can be disposed in or on a wiper arm, not otherwise shown. The longitudinal conduits can also receive heating lines for heating up the washing fluid.
To make the connection part with a central bore simple in design, it is expedient to provide the adapter piece of zinc with longitudinal conduits and extend it through the connection part The adapter piece can have an outward-pointing head, to which conduits leading onward can easily be connected.
A similar fastening technique as for the connection part can also be used for the crank. Here it is expedient that the base body, on the end toward the crank, has a region with fluting in the longitudinal direction, over which fluting the crank of a harder material is cast with the base body.
To avoid contact corrosion among the various components of the drive shaft, it is advantageous that the base body and the connection part or the crank are chemically nickel-plated after being joined together.